#🔒 subdivide a txt file
analog heath
@frigid wharf You can't upload files here. Use a paste link if you'd like to share code
!paste
abstract inletBOT
analog heath
Not a problem!
frigid wharf
https://paste.pythondiscord.com/3PBA I have this txt file with some fake data in it
I have to work with it and do operation like "print all student in base of theyr age"
"order in alphabetical order" "print users in base of class"
analog heath
What code have you written so far?
frigid wharf
What code have you written so far?
Not much (zero)
analog heath
Is there anything from this you do know how to do?
frigid wharf
I don't know where to start
frigid wharf
Is there anything from this you *do* know how to do?
I know I can open txt file with open file as f
analog heath
That's a good place to start
frigid wharf
I know the functions read, readline and readlines
I know the basic built in function such as split()
analog heath
it's always best to dive in with what you do know and then you can work around any issues you have
but a blank python document is far scarier
analog heath
start with opening the file
frigid wharf
I have it opened
analog heath
with python
frigid wharf
Yes
analog heath
ok, and you said you know how to split, so split the lines of the file
frigid wharf
ok, and you said you know how to split, so split the lines of the file
I know I can split a list
analog heath
you can't split a list
analog heath
you can split a string into a list
frigid wharf
Yeah sorry
analog heath
!e
line = '1 B LUCA CAVALLI 14/04/2007'
print(line.split())
@analog heath :white_check_mark: Your 3.12 eval job has completed with return code 0.
['1', 'B', 'LUCA', 'CAVALLI', '14/04/2007']
How can I use this?
analog heath
so for example, here's one line of your file
frigid wharf
Oh wait I have an idea
analog heath
this perfectly splits it into number, letter, first name, last name, date
frigid wharf
line = f.readline()
line.split()
analog heath
since you're going to want to want every line, you're better off using readlines()
that will load all the lines into a list which you can then iterate
or even for line in f:
frigid wharf
But readlines give me a list
analog heath
yes, which you can use a for loop with
frigid wharf
Oh I can out it in a for and take thing
And then take the first element (class) and put in a class list?
analog heath
there's no need to separate the elements
one student is represented in 1 line of text
you can have a list of lists of students
This is eventually what you want to end up with
a list of lists
frigid wharf
oh its alredy subdived
analog heath
I'm not sure what you mean by that?
I'm showing you the result you want to get. There's a few steps required to get to this point
frigid wharf
lets say i want to print the name in order
analog heath
don't worry about the ordering yet
frigid wharf
oh its not alredy did with readlines?
analog heath
we're focusing on one thing at a time
analog heath
oh its not alredy did with readlines?
no, readlines access each line. You still need to split each line to get the data within
frigid wharf
i honestly dont know how to do it
analog heath
with readlines and split
frigid wharf
i have an idea but it seems usless
analog heath
you said you know how readlines works, and how split works
always show what you try
and always try
frigid wharf
with readlines and split
readlines give me a list, i cant split a list
analog heath
Oh I can out it in a for and take thing
.
you've already said what you need to do with that list
you have a list of strings
analog heath
readlines gives you a list of strings
frigid wharf
we will work with it
analog heath
you can use a for loop on that list
yes, it's very hard to help you adjust code if you aren't sharing it
frigid wharf
sorry
cold hull
thats line.split(" ") for each line aint it
analog heath
thats line.split(" ") for each line aint it
yup!
It's being appended to a new list as well to store them
I'd like to walk through the logic of a for loop without list comp for now
frigid wharf
tbh i didnt understand
analog heath
show what you tried
you said you understand readlines, and split, so it's hard to figure out what part you're stuck at
cold hull
split it into lines and iterate over that
frigid wharf
i was trung to work with one line at time to test
analog heath
That's a good start
you can access every line in a file by simply doing for line in file
so if you had a for loop that does this, you don't really have to change much else about your code
frigid wharf
the code dosent seem to work
analog heath
yes, it works perfectly for 1 line
frigid wharf
why the space becomed \t?
analog heath
oh
frigid wharf
yes, it works perfectly for 1 line
dosent seem
frigid wharf
why does it do this?
frigid wharf
tabs are "\t"
oh
give me a second i have an huge idea
ok it dosent work
lines = [] # empty matrix
with open("dati_alunni.txt", "r") as file:
for i in range(len(file.readlines())):
line = file.readline() # read line by line
if line != "": # for empty lines
line.split() # split in list
lines.append(line) # add list to matrix
print(lines)```this is my code, lines is an empty list
analog heath
no need to use range here
frigid wharf
i never used a for without it, so idk
analog heath
and no need to use readline AND readlines
I've mentioned multiple times above how you can use it
analog heath
or even `for line in f:`
.
frigid wharf
i understand but if i copy code you can do my homework and send directly to the teacher
i want to understand, not to copy things
analog heath
that's why I'm not handing you the solution
but I'm hoping you can piece together what I'm telling/showing you
loop through file
split line
append line to list of students
that's all you need to do, you're overthinking it a bit
frigid wharf
i have an idea
lines = [] # empty matrix
with open("dati_alunni.txt", "r") as file:
for line in file.readlines():
if line != "": # for empty lines
line.split("\t") # split in list
lines.append(line) # add list to matrix
print(lines)```but it dosent work
analog heath
when you do line.split, it simply returns the new list, it won't actually modify the data that line represents
you can either create a new variable, or append it in 1 line
lines.append(line.split())
frigid wharf
oh yeah i am stupid i forgot
analog heath
I still really recommend using split() instead of split("\t")
analog heath
yes, you have a list of lists now
I'd also recommend naming your variable something a bit different so it's less confusing
students might make more sense than lines
always try and be meaningful with your var names
frigid wharf
i have one idea to continue
frigid wharf
always try and be meaningful with your var names
yeah sorry, i usually do that
but sometimes i forgot if the code is small
students_info = [] # empty matrix
with open("dati_alunni.txt", "r") as file:
for line in file.readlines():
if line != "": # for empty lines
line = line.split() # split in list
students_info.append(line) # add list to matrix
print(students_info)```what do i do now?
something that i know is the fact that in this matrix the first element of each list is always the class
the second the section etc
so if i do students_info[i][j]
and put i/j with a fixed value
i can get all the row
am i right?
analog heath
something that i know is the fact that in this matrix the first element of each ...
exactly, this is very useful
do you know how to sort a list?
frigid wharf
yes
.sort(order, key)
first thing that i want to do its to sort all the names, right?
analog heath
do you know how to use the key?
frigid wharf
i dont think i need it
analog heath
you do need it if you want to sort by names
frigid wharf
my idea was a little different
since i dont know how to use key (i never used it in class, i just know it exist) i was thinking to use ascii
analog heath
the key is how we can tell python by which information to sort the list
in this case, we can use the key to tell it to sort by name
frigid wharf
how can we use it?
analog heath
and do you know what return does in a function?
analog heath
ok, so when we use key to sort something, we're basically telling it a specific function to call on every item in the list. The list will then be sorted by the return of this function
['1', 'A', 'VIOLA', 'ROSSI', '12/05/2007']
do you want to sort by last name or first name?
frigid wharf
last name
analog heath
ok, which index of this list is that?
frigid wharf
3
analog heath
exactly
def sort_last_name(student):
you can define a function like this which we'll eventually use as the sort key
the information it will receive is 1 student (a list of information about that student)
if we return student[3], we're telling it each student should be sorted by last name
def sort_last_name(student):
return student[3]
everything is already exactly as it should be up until this point
you don't have to do any more splitting
frigid wharf
!e
lista = ["banana", "mela", "pera", "arancia"]
print(lista.sort())```@frigid wharf :white_check_mark: Your 3.12 eval job has completed with return code 0.
None
there's 2 ways to sort
.sort() and sorted()
.sort() simply sorts the list "in place"
sorted() returns a new list that is sorted
ideally you would actually use sorted() here
frigid wharf
!e
lista = ["banana", "mela", "pera", "arancia"]
print(sorted(lista))```@frigid wharf :white_check_mark: Your 3.12 eval job has completed with return code 0.
['arancia', 'banana', 'mela', 'pera']
yes, strings will be sorted alphabetically (although it is case sensitive)
but this is one list of strings
we have a list of a list of strings for the students
frigid wharf
why lista.sort() is none and sorted(lista) not?
analog heath
because sort() doesn't return anything
it's an "in place" operation
it "mutates" the list
!e
lista = ["banana", "mela", "pera", "arancia"]
lista.sort()
print(lista)
@analog heath :white_check_mark: Your 3.12 eval job has completed with return code 0.
['arancia', 'banana', 'mela', 'pera']
Oh ok
I have to options: use the key or make a list with all names
Right?
Sorry for late reply
analog heath
you could, but that's extra steps
plus what if you want to sort by last name, but still display the rest of their information?
frigid wharf
Because key is a little bit hard to understand
analog heath
def sort_last_name(student):
return student[3]
students = []
with open("people.txt", "r") as file:
for line in file:
students.append(line.split())
for student in sorted(students, key=sort_last_name):
print(student)
Here is everything in action
the function that will be used for sorting is defined at the top
sorted(students, key=sort_last_name)
I don't say that you explanation is bad, just that I don't really understand it much
analog heath
if my explanation was good, you would understand it 🙂
frigid wharf
if my explanation was good, you would understand it 🙂
i didnt, sorry..
cold hull
sort when sorting uses the value returned by the key function for that value so for example the list [1,2,3] with the key def key(x): x[1] vould be sorted as if its value was 2
sorted returns the list list.sort(key=) will sort the list in place and return none thus list.sort()'s value is None but in the place of the original list there will be a sorted list and with sorted sorted()'s value is the sorted list and the original list is unchanged
frigid wharf
i honestly didnt understand anything this time
i think its because fo my poor english skills
abstract inletBOT
Python help channel closed